Apparatus for establishing electrical contact with the casing in a wellbore

ABSTRACT

An apparatus for establishing electrical contact with the casing within a well bore. A plurality of flexible support members each have their first end attached to a central shaft and their second end attached to a collar slidably engaging the shaft. An electrical contact wheel is mounted on each support member. A fixed shaft collar restrains a spring which biases the slidable collar, causing the support members to flex, thereby urging the contact wheels outwardly to contact the well casing.

Wm? R 335683053 [72] Inventors JamesM.Ki!patl-lck [56] RefimcesClied Claremore; h UNiTl-ID STATES PATENTS [m A IN f g 'f' 2,307,337 1/1943 Haynes 324/x {22] fg 1968 2,427,950 9/1947 Bah 324/10 mm d M 2,517,603 3/1950 Silverman... 324/10x [73] mi 2 jz 2,633,485 3/1953 Pamode 324/10 g e 3,077,670 2/1963 Waters 324/10x New York, N.Y.

Primary Examiner-Edward E. Kubasiewicz Attorney-Alden, Mono-e and Boustead ABSTRACT: An apparatus for establishing electrical contact with the casing within a well bore. A plurality of flexible support members each have their first end attached to a central [54] APPARATUS FOR ESTABLISHING ELECTRICAL CONTACT WITH TEE CASING IN A WELLBORE 4 5 Claims 2 nnwiqgags shaft and their second end attached to a collar slidably engag- [52] US. 324/62, ing the shaft. An electrical contact wheel is mounted on each 324/ l0 support member. A fixed shaft collar restrains a spring which [51] Int. Cl. 60111 27/02 biases the slidable collar, causing the support members to flex, [50} Field of Search 324/ (P), thereby urging the contact wheels outwardly to contact the I0, 62, 64 well casing.

"vmimamn 2m 7 3.568053 mvmmns JAMES M KtLPATRlCK 8 ROBERT E. WALKER APPARATUS FOR ESTABLISHING ELECTRICAL CONTACT WITH THE CASTNG IN A WELLBORE The present invention pertains to a downhole tool for use within a well casing or other pipe. More particularly, the present invention pertains to such a tool used to establish electrical contact within the well casing.

In many operations, for example corrosion determination, it is desired to establish electrical contact at a point within a well casing. In corrosion determination, for example, electrical contact is established with the well casing at two or more locations at different depths within the well separated by a known distance. The difference in electrical potential between the two locations provides information useful in corrosion determination.

While well bore tools including motor driven blades which contact the well casing to establish electrical continuity are known, such apparatus are cumbersome to use, in addition to being expensive. Other well bore tools include blades which are held in a retracted position until the apparatus is lowered to the bottom of the well bore, at which time the blades are released to contact the well casing. Electrical readings are made as the apparatus is raised in the well bore. With the blades in their extended position, the apparatus cannot be lowered within the well bore. Consequently, if a location at which a reading is desired is inadvertently passed, the apparatus must be lifted from the well, the blades returned to their retracted position, and again the apparatus lowered into the well to the desired depth. This is an extremely time consuming operation. Due to the great depths at which readings are desired within a well bore, removal of the apparatus from the well and return of the apparatus to the desired depth might require several hours.

Anothertype of well bore tool can be lowered to a desired level within the well bore, and, by a quick lifting motion,

' blades are released to contact the well casing. The apparatus can be moved upward within the well bore by simply raising it. When it is desired to lower it, another quick lifting motion causes the blades to be retracted so that they no longer contact the well casing, and then the apparatus can be readily lowered. This apparatus is complex and subject to malfunctioning of the blade releasing and retracting apparatus.

The present invention is an apparatus for establishing electrical contact with a well casing at a desired depth within a well bore. Even after electrical contact is made the location of the apparatus can readily be raised or lowered without removing the apparatus from the well bore. The apparatus includes a plurality of contacting wheels mounted on flexible supports about a central shaft. One end of each flexible support is rigidly attached to the central shaft, while the second end of each flexible support is attached to a spring biased collar. Under the urging of the spring, this collar tends to cause the supports to flex, thereby, moving the contact wheels outward until they establish contact with the well casing.

These and other aspects and advantages of the present invention are apparent from the following detailed description and claims, particularly when considered in conjunction 'with the accompanying drawings which depict one preferred embodiment of the apparatus and in which like parts bear like reference numerals.

ln the drawings:

FIG. 1 is a vertical sectional view of a well bore and well casing depicting a well logging apparatus in accordance with the present invention; and

HO. 2 is a fragmentary elevational view of the well contact assembly of the present invention.

FIG. 1 depicts a well logging apparatus suspended by wire lines 11 within well casing 12 in well bore 13 which extends into the earth formation 14. Well logging apparatus 10 includes first and second contacting assemblies 16 vertically spaced on shaft 13. By means of well logging apparatus 10 conventional corrosion measurements can be made within well casing 12 in a well-known manner. Thus, for example, the

electrical potential as different depths within the well casing 12 might be measured and recorded utilizing the two contact assemblies 16 which are vertically separated by a known distance, for example. a distance in the order of 20 feet. The electrical potential s' gals obtained from each contact assembly 16 are transmitted by means of electrical cables 20 which pass through shaft 18 and wire line 11 to conventional electrical equipment 21 at the earth's surface. One electrical cable 29 connects to apper contact assembly 16 at its contact point 17. A second eleztzical cable 20 connects to lower contact assembly 16 at contact point 17. A third electrical cable 20 connects to lower end 19 of shaft 18 at its contact point 23. The two correct assemblies 16 and lower end 19 are electrically insulated each other and from the remainder of apparatus 10 by irssrlating members 25. While FIG. 1 depicts two contact :ssmolies 16 mounted on shaft 18, for some operations there might be additional contact assemblies further down well casing 12. Additionally, a shaft 18 may extend the length of on" one contact assembly l6, and two or more such assemblies l6 may be suspended from wire line 11 at different depths well casing 12.

Ad depicted in FIG. 2 one end of each contact assembly 16 is rigidly attached to s'tafi 18 by means of a centralizing retaining collar 22 which is attached to shaft 18 by suitable means such as bolts. Four flexible supports 24, which, for example, might be centralizing springs, each have one end attached to collar 22. An electrical contact wheel assembly 26 is mounted to the second end of each support 24. A second flexible support 28 is likewise anzched to each contact wheel assembly 26. The second end of each support 28 is attached to centralizing collar 30 which slidably engages shaft 18. Spring retaining collar 32 is r'gidly mounted to shaft 18 and supports biasing means such as coil spring 34 which encircles shaft 18 between collars 30 and 32. Spring 34, for example, might be a coil spring having a lezgth in the order of four inches and having one or more turnsof wire ofa diameter in the order ofonefourth inch. Each wheel assembly 26 includes a knife wheel 36 mounted for rotation within bracket 38.

When it is desired :1 establish contact with well casing 12, apparatus 10 is lowered into the well bore. One end of spring 34 is restrained by c 32, while the second end ofspring 34 acts against collar 36'. Under the urging of spring 34, collar 30 is biased, tending to move towards fixed collar 22, thus causing flexible supports 34 and 28 to push contact assemblies 26 outward until they osntact well casing 12. Accordingly the contact assemblies 26 are held firmly against the inside of the well casing to establiziz good electrical contact. The location of spring retaining coTar 32 can be changed to vary the compression of coil spring 34. As each assembly 16 traverses the well casing, its supports 24 and 28 flex to permit passage through any restrictices that might be within the well casing and that otherwise w-mld block passage of the assembly. Each contact assembly 16 then transmits via its associated insulated cable 20 to electrical equipment 21 signals indicative of the electrical potential at is location within well casing 12, in accordance with known well logging procedures. The insulator 25 separating lower contact assembly 16 from lower end 19 results in electrical equipment 21 indicating an infinite resistance between those two members. Should apparatus 10 come into contact with water within well casing .12, this resistance drops to a vet low value, and electrical equipment 21 so indicates. Accordingly, it is indicated that the apparatus has reached water at well casing 12, and the apparatus can be raised to insure it is natdamaged by the water.

We claim:

1. Well logging apparatus comprising suspension means for insertion into a well casing, a plurality of electrical contact apparatus carried by suspension means,-each electrical contact apparatus comprising shaft means, flexible support means having first and secorri ends, a rotatable cutting and electrical contact means intermediate the support means first end and the support means second end, first retaining means fixedly attaching the support 6308 first end to the shaft means and having no moving parts, second retaining means fixedly attached to the shaft means, engaging means attached to the support means second end for slidably engaging the shaft means, biasing means having a first end restrained by the second retaining means and having a second end contacting the engaging means for biasing the engaging means toward the first retaining means to cause the flexible support means to flex to move said rotatable cutting and electrical contact means outwardly from the shaft means, insulation means electrically insulating each electrical contact apparatus from the rest, electrical circuit means connecting said electrical contact means in series including from one rotatable cutting and electrical contact means in one electrical contact apparatus through a portion of said well casing to an adjacent rotatable cutting and electrical contact means in a separate electrical contact apparatus, and electrical equipment means operatively connected to said circuit means for registering the electrical poterstal ofthe portion of the well casing included in said series comedian.

2. Apparatus as chimed in claim 1 in which each flexible support means includes a plurality of flexible support members each supporting aratatable cutting and electrical contact UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIGN Patent No. 3,568,053 Dated March 2, 1971.

lnventofls) James M. Kilpatrick and Robert E. Walker It is certified that error appears inthe above-identified patent and that said Letters Patent are hereby corrected as shown below:

F Column 2, line 22, "Ad" should read -As-- Insert the following claim at column 4, line 15:

6. Apparatus as claimed in claim 1 further including a bottom end member suspended beneath the lower most electrical contact apparatus and electrically insulated therefrom, and means for indicating the resistance. between said bottom end member and said lowermost electrical contact apparatus so that said resistance indication changes when said bottom end member is immersed for the first time in a liquid.

On the cover sheet [54] "5 Claims should read 6 Clai Signed and sealed this 3rd day of August 1971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SGHUYLER, JE Attesting Officer Commissioner of Patent: 

1. Well logging apparatus comprising suspension means for insertion into a well casing, a plurality of electrical contact apparatus carried by said suspension means, each electrical contact apparatus comprising shaft means, flexible support means having first and second ends, a rotatable cutting and electrical contact means intermediate the support means first end and the support means second end, first retaining means fixedly attaching the support means first end to the shaft means and having no moving parts, second retaining means fixedly attached to the shaft means, engaging means attached to the support means second end for slidably engaging the shaft means, biasing means having a first end restrained by the second retaining means and having a second end contacting the engaging means for biasing the engaging means toward the first retaining means to cause the flexible support means to flex to move said rotatable cutting and electrical contact means outwardly from the shaft means, insulation means electrically insulating each electrical contact apparatus from the rest, electrical circuit means connecting said electrical contact means in series including from one rotatable cutting and electrical contact means in one electrical contact apparatus through a portion of said well casing to an adjacent rotatable cutting and electrical contact means in a separate electrical contact apparatus, and electrical equipment means operatively connected to said electrical circuit means for registering the electrical potential of the portion of the well casing included in said series connection.
 2. Apparatus as claimed in claim 1 in which each flexible support means includes a plurality of flexible support members each supporting a rotatable cutting and electrical contact means.
 3. Apparatus as claimed in claim 2 in which each rotatable cutting and electrical contact means comprises a knife wheel rotatably mounted on its associated flexible support member.
 4. Apparatus as claimed in claim 3 including four flexible support members and four knife wheels.
 5. Apparatus as claimed in claim 3 in which the biasing means includes coil spring means. 